const fp = require('lodash/fp')

// 数据
// horsepower 马力, dollar_value 价格, in_stock 库存

const cars = [
    { name: 'Ferrari FF', horsepower: 660, dollar_value: 700000, in_stock: true },
    { name: 'Spyker C12 Zagato', horsepower: 650, dollar_value: 648000, in_stock: false },
    { name: 'Jarguar XKR-S', horsepower: 550, dollar_value: 132000, in_stock: false },
    { name: 'Audi R8', horsepower: 525, dollar_value: 114200, in_stock: false },
    { name: 'Aston Martin One-77', horsepower: 750, dollar_value: 185000, in_stock: true },
    { name: 'Pagani Huayra', horsepower: 700, dollar_value: 130000, in_stock: false },
]

let isLastInStock = function (cars) {
    let last_car = fp.last(cars)
    return fp.prop('in_stock', last_car)
}

// 练习1：使用函数组合fp.flowRight()重新实现下面这个函数

let isLastInStock_composed = fp.flowRight(fp.prop('in_stock'), fp.last)

// 练习2：使用fp.flowRight()、fp.prop()、fp.first()获取第一个car的name

let firstCarName = fp.flowRight(fp.prop('name'), fp.first)(cars)

// 练习3：使用帮助函数_average重构averageDollarValue，使用函数组合的方式实现

let _average = function (xs) {
    return fp.reduce(fp.add, 0, xs) / xs.length
}

let averageDollarValue = function (cars) {
    let dollar_values = fp.map(function(car) {
        return car.dollar_value
    }, cars)
    return _average(dollar_values)
}

// 重构后
let averageDollarValue_composed = fp.flowRight(_average, fp.map(fp.prop('dollar_value')))

// console.log(averageDollarValue(cars))
// console.log(averageDollarValue_composed(cars))

// 练习4：使用flowRight写一个sanitizeNames()函数，返回一个下划线连接的小写字符串，把数组中的name转换为这种形式：例如：sanitizeNames(['Hello World']) => ['hello_world']

let _underscore = fp.replace(/\W+/g, '_')

let sanitizeNames = fp.map(fp.flowRight(_underscore, fp.lowerCase))

// console.log(sanitizeNames(['Hello World']))